Sterilant system

ABSTRACT

A two-part sterilant system comprises a first part comprising a first reagent in a carrier medium and a second part which is miscible with the first part and which comprises a second reagent in a carrier medium. The first reagent and the second reagent will react when mixed to provide a sterilising composition. The first part is contained in a pump dispenser ( 2 ) whereby it may be dispensed as a fluid, and the second part is absorbed or impregnated in at least one fabric member ( 18 ) in a sealed container ( 20 ).

This application is a continuation application of U.S. application Ser.No. 10/935,651, filed 7 Sep. 2004, and which application is incorporatedherein by reference. To the extent appropriate, a claim of priority ismade to U.S. application Ser. No. 10/935,651.

FIELD OF THE INVENTION

The present invention relates to a two-part sterilant system, notably toa system for producing chlorine dioxide (ClO₂). The invention isparticularly for use in sterilising medical supplies and equipment, butit is not limited to these uses.

BACKGROUND TO THE INVENTION

Two-part sterilising solutions are used in applications where the activesterilising ingredient is unstable over time. The solution is thereforeprepared in situ shortly before it is to be used. A particularlyimportant sterilising agent is chlorine dioxide, which may be formedfrom mixtures of various reagents including: chlorite and acid;chlorate, peroxide and acid; and chlorite, hypochlorite, and a suitablebuffer. Chlorine dioxide has excellent sterilising and bactericidalproperties, and oral ingestion in man and animals has been shown to berelatively safe.

The cleaning of endoscopes and other medical equipment with suitablechlorine dioxide solutions is known from earlier patents in the name ofthe present inventor, for example, European Patent Number 0 785 719 andU.S. Pat. Nos. 5,696,046 and 6,007,772, the contents of which are herebyincorporated by reference.

It is not always convenient to mix up batches of solutions for use insterilising equipment. For wiping down (rather than thoroughly cleaninginside and out) of endoscopes and probes, wipes of alcohol,general-purpose detergent, or soapy water are generally used, but theseare not as effective as chlorine dioxide. It is desirable to be ablereadily to make up small quantities of two-component sterilising agentswhen desired and to be able to make such agents up in a form in whichthey may be readily handled for a particular application.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided atwo-part sterilant system comprising:

(a) a first part comprising a first reagent in a carrier medium; and(b) a second part which is miscible with the first part and whichcomprises a second reagent in a carrier medium;

-   -   wherein the first reagent and the second reagent will react when        mixed to provide a sterilising composition;    -   characterised in that the first part is contained in a pump        dispenser whereby it may be dispensed as a fluid, and in that        the second part is absorbed or impregnated in at least one        fabric member in a sealed container.

The term “fluid” is used herein to include liquids, foams, sprays,pastes, aerosols, powders, sols and gels. It is particularly preferredthat the first part is dispensed as a foam or a spray to facilitate itscoverage of a desired area of the fabric member. Optionally, thedispenser may have a relatively large dispensing head, for supplying thefluid over all or a substantial part of a surface of the fabric member.For example, the dispensing head may take the form of a rose orsprinkler with a multitude of small orifices to spread the fluid overthe fabric member.

The pump dispenser is preferably a trigger-operated dispenser, both forconvenience and to facilitate the dispensing of metered quantities.However, other pump dispensers could be used, for example, a squeezebottle with a suitable spray or foam nozzle. The invention will, forconvenience, be described hereinafter with reference to the use of atrigger-operated dispenser, but it is to be understood that it is notlimited to this embodiment.

By putting up the first part in a trigger-operated dispenser, smallquantities may be readily dispensed without risk of spillage. Preferablythe dispenser comprises a sprayer apparatus that provides the first partas a foam so that it is at least partly form-retaining and can bereadily seen and manipulated. We have also found that providing thefirst part in a foam may have the beneficial effect of reducing theodour of chlorine dioxide when the wipe is activated. The invention willfor convenience be described with reference to this preferredembodiment, but it will be understood that the invention is not limitedto this embodiment.

The trigger sprayer may include a mixing chamber to facilitate mixing ofthe first part with air, for example as described in U.S. Pat. No.5,337,929.

The fabric members may be formed from any suitable fabrics, either wovenor non-woven. They may be of natural or man-made fibres, for examplepolyester, cotton, cellulose or mixtures thereof. Other suitable fabricswill be well known to those skilled in the textile or fabric arts.

The fabric member may comprise a fabric wipe or cloth, or a gauze, pad,or other wound dressing material. Once prepared, the fabric member willhave biocidal properties and may be used to dress wounds, ulcers, or thelike while promoting a sterile local environment around the wound. Forconvenience, the invention will be described hereinafter with referenceto the use of a fabric wipe, but it is to be understood that theinvention is not limited to this embodiment.

By providing the second part absorbed in a fabric wipe, a sterilisingwipe may readily be prepared by applying the first part to the wipe. Theuser may fold the wipe or rub two halves together to facilitate mixing.The wipes are particularly useful for cleaning, disinfecting, andsterilising surfaces and equipment, notably in a medical environment.

The first part may include a coloured component so that a visualindication of the coverage of the wipe with the first part can be made.

In a preferred embodiment, at least one of the first and second parts isprovided with an indicator reagent that changes colour to show thatsufficient mixing has taken place. Where the first part and the secondpart are of different pH, the indicator may be a pH-sensitive indicator.Suitable indicators are well known to those skilled in the art,non-limiting examples including: phenol red, litmus, thymol blue,pentamethoxy red, tropeolin OO, 2,4-dinitrophenol, methyl yellow, methylorange, bromophenol blue, tetrabromophenol blue, alizarin sodiumsulphonate, α-naphthyl red, p-ethoxychrysoidine, bromocresol green,methyl red, bromocresol purple, chlorophenyl red, bromothymol blue,p-nitrophenol, azolitmin, neutral red, rosalic acid, cresol red,α-naphtholphthalein, tropeolin OOO, phenolphthalein, α-naphtholbenzein,thymolphthalein, nile blue, alizarin yellow, diazo violet, tropeolin O,nitramine, Poirrer's blue, trinitrobenzoic acid, and mixtures thereof.It is preferred that the indicator is selected so that both parts areseparately colourless and the colour develops when the two parts aremixed.

Alternatively, or additionally, one or more fluorescent additives may beincluded so that the mixture fluoresces to indicate mixing. Non-limitingexamples of suitable fluorescing agents include: 4-methylumbelliferone,3,6-dihydroxanthone, quinine, thioflavin, 1-napthol, harmine, coumarin,acridine orange, cotarmine, and mixtures thereof.

The indicator (colour change or fluorescent) may be included in eitherpart. Preferred proportions by weight are about 0.1 to 10%, notablyabout 0.5 to 2%.

The carrier mediums may be fluids such as liquids or sols, or they maybe more form-retaining or viscous compositions such as gels or pastes.It is preferred that at least one reagent is present in an aqueousfluid, although other additives may of course be present. Preferablyboth reagents are put up in aqueous fluids.

The trigger-operated dispenser may be a conventional atomiser or foamer,or other manual pump in which the contents are expelled manually byoperation of the trigger by the user. Alternatively, the dispenser maycontain a propellant to dispense the contents when operation of thetrigger opens a valve, as is well known in applications such as shavingfoam canisters and the like. Suitable dispensers will be well known tothose skilled in the art.

The preferred sterilising agent is chlorine dioxide, which may be formedfrom suitable known reagents. In a preferred embodiment one reagent is achlorite (notably sodium chlorite) and the other is an acid, preferablywith a buffer. Suitable acids include lactic acid, citric acid, boricacid, phosphoric acid, acetic acid, sorbic acid, ascorbic acid,hydrochloric acid or mixtures thereof. In a preferred embodiment amixture of acids is used, notably a mixture of citric, sorbic and boricacids.

A particularly preferred system is as described in EP 0 785 719, withthe corrosion inhibitors optionally not included, and with otheradditives as desired for particular applications. In addition tosuitable indicators, optional additives include foam-promoting agents orstabilisers, humectants, essential oils and fragrances. Othersterilising agents may also be employed; for example chlorine or oxygen.Chlorine may be produced by reaction between a hypochlorite such assodium hypochlorite, and a suitable acid or buffer. Oxygen may beproduced by reaction between a peroxide and a catalyst such as catalase,optionally in the presence of a buffer. For convenience hereinafter, theinvention will be described with reference to chlorine dioxide as thesterilising agent.

Suitable foam promoters will be well known to those skilled in the art.Non-limiting examples include: sodium laureth sulphate, ammonium laurylsulphate, cocamide DEA, cocamidopropyl betaine, sodium laurylsarcosinate, cocamidopropylamine oxide, monoethanolamine laurylsulphate, cocamidopropyl hydroxysultaine, cocoyl sarcosinate. Anionic,cationic, non-ionic and amphoteric surfactants may be employed dependingon the chemistry of the reagents. The foam promoters are selected toprovide a stable foam structure. The foam promoter may comprise fromabout 0.1 to 50% by weight of the first part, notably from about 1 to10%, preferably from about 3 to 6%.

Suitable foam stabilisers well known to those skilled in the art mayalso be used, in proportions similar to those for the foam-promoters.Non-limiting examples include: alkanolamides, for examplemonoethanolamides and diethanolamides, amine oxides, betaines, proteinhydrolysates and cellulose derivatives such as carboxymethylcellulose.

In a preferred embodiment, a humectant is included in at least one ofthe first and second parts. Humectants serve to reduce the rate ofevaporation of components and improve product feel if direct skincontact is involved. We have found that the use of a humectant reducesthe volatility of chlorine dioxide, which reduces the odour of chlorinedioxide and prolongs the life of the activated mixture. Non-limitingexamples of suitable humectants include sodium lactate and polyols, forexample glycerine, sorbitol, propylene glycol, diethylene glycol andethylene glycol. The humectant may be present in any desired amount,particularly from about 0.1 to 50% by weight, notably from about 0.5 to10%, preferably from about 1 to 3%.

Where one of the reagents is basic or oxidising, for example sodiumchlorite, it is particularly preferred that this reagent is provided inthe trigger dispenser rather than in the wipe, because such reagents mayreact with the fabric over time. Preferably the optional humectant isincluded in the first part, with the sodium chlorite or other firstreagent.

The first and/or second part may further include a biocide to ensurethat, in the event of poor mixing of the parts, a biocidal effect isstill present. The first and/or second part may also include apreservative.

Equal weights of the first part and the second part may provide, whenmixed, a sterilising composition having a pH of from 1.0 to 10.5, but itis preferred that the composition has a pH of from 4.5 to 6.5 as thismay result in a more stable compound.

A plurality of fabric members may be provided in a single resealablecontainer, for example a canister with a lid, or a resealable sachet. Ina preferred embodiment, each fabric member is provided in its own sachetwhich may be factory-sealed and disposed of after use. In a particularlypreferred embodiment, each sealed sachet contains a single fabric wipe.

Other aspects and benefits of the invention will appear in the followingspecification, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example, withreference to the following drawings in which:

FIG. 1 shows a trigger sprayer for use in a sterilant system inaccordance with an embodiment of the present invention;

FIGS. 2 and 4 show an canister of sterilising wipes, respectively openand closed, for use in a sterilant system in accordance with anembodiment of the present invention;

FIG. 3 shows an alternative trigger sprayer for use in a sterilantsystem in accordance with an alternative embodiment of the invention;and

FIG. 5 illustrates a sterilant system in accordance with a furtherembodiment of the invention.

DETAILED DESCRIPTION

The trigger sprayer shown in FIG. 1 is of a construction well known perse. The sprayer comprises a body 2 connected to a sprayer head 4 by aninternally screw-threaded connector ring 14. A spray nozzle 10 in thehead is connected to an aqueous liquid 12 by means of a dip tube 6. Auser dispenses the liquid 12 through the nozzle 10 by operation of atrigger 8. Rotation of the nozzle allows the user to dispense the fluidas either a spray of fine droplets or as a foam.

In the present example, the liquid 12 (first part) comprises 0.75% of afirst reagent (sodium chlorite), 3.0% foam promoter (CocamidopropylBetaine). The remainder is deionised water. In this specification, allparts are by weight unless otherwise indicated. Operation of the trigger8 dispenses the first part 12 as a foam.

An alternative design of pump dispenser 2 is illustrated in FIG. 3. Thetrigger 8 is formed integrally with the nozzle 10. Depressing thetrigger 8 dispenses a portion of the fluid contents as a foam (referredto as the ‘Activator Foam’ because it activates the sterilising powersof a sterilising wipe). A protective cap 26 is provided to cover thenozzle 10 and trigger 8 when not in use.

Turning now to FIGS. 2 and 4, a sealable container 20 is also of aconstruction well known per se. The container 20 is a hollow cylinderfitted with a cap 22. The container 20 contains a roll of interleavedfabric sheets 18. In this example, the fabric sheets 18 are to be usedas sterilising wipes, but it will be understood that the sheets 18 couldalso be used for other applications such as biocidal wound-dressings.

The cap 22 has a central opening through which a tip of the central wipe18 is disposed. By pulling the central wipe 18, a user may remove thiswipe from the container, leaving the next wipe in its place. A stopper16 is provided on the cap 22 for releasably sealing the container 20.

In this example, the wipes 18 are impregnated with an aqueous acidsolution (second part). In this example, the acid solution comprises0.5% citric acid, 0.05% sorbic acid, 0.05% boric acid. The solution alsocomprises 0.35% of a buffer (trisodium phosphate). The solution alsocomprises 0.25% Trisodium Citrate, 1.0% glycerine, 0.1% Benzotriazole,0.1% Sodium Molybdate and 0.3% Sodium Nitrate. The remainder isdeionised water.

The pump dispenser 2 and container 20 together comprise the sterilantsystem. To prepare a sterilising wipe, a user removes an impregnatedwipe 18 from the container 20, and applies a portion of foam from thesprayer 2 to the wipe 18. To facilitate mixing of the reagents in thefoam and the wipe, the user may fold the wipe in half and crush or rubthe folded wipe before opening it out. Preferably, one of the componentsis provided with a pH-sensitive indicator which changes colour orbecomes coloured when adequate mixing has occurred, thereby indicatingthat sufficient ClO₂ has been generated in the wipe.

Once the sterilising wipe has been prepared, it may be used for a numberof applications, including wiping surfaces and sterilising medicalequipment such as endoscopes.

In the preferred embodiment illustrated in FIG. 5, each sterilising wipe18 is provided in its own sealed container 20, in this example a sachet.The sterilant system comprises a box 28 of sterilising wipes 18 inindividual sachets 20. Each sachet 20 may be factory sealed and may bedisposed of after the wipe has been removed. The foam pump dispenser 2is also provided in the box 28 of sterilising wipe sachets 20.

EXPERIMENTAL RESULTS Experiment 1

Sterilant wipes in accordance with one embodiment of the invention weretested and compared with conventional wipes saturated with isopropanol(IPA), a general-purpose detergent, and sterile deionised water.

The test method to evaluate effectiveness of the wipes inkilling/removing test organisms dried onto test surfaces, involved thefollowing steps.

1. Mark out a six inch (30.5 cm) square test area on the test surface.

2. Inoculate the test surface with 0.5 ml of test organism suspension.

3. Spread the inoculum over the test area using a plastic spreader.

4. Allow the inoculum to dry (about 30 minutes).

5. Don a pair of disposable plastic gloves.

6. Prepare a ClO₂ wipe in accordance with the invention, using aprescribed mixing time.

7. Wipe the test area for the prescribed wiping time.

8. Place the wipe in 10 ml of universal neutraliser in a Universalbottle (Test Suspension A). Vortex stir to release organisms.

9. Wipe the entire test area with a cotton-tipped swab (thoroughly/10times).

10. Dip the swab into 10 ml of universal neutraliser in a Universalbottle after each sampling of the test area and rotate the swab againstthe inner wall of the bottle to release organisms (Test Suspension B).

11. Prepare 5 serial deci-dilutions of Test Suspension A and TestSuspension B in diluent.

12. Inoculate 0.5 ml of each dilution onto a culture plate and spreadusing a plastic spreader. Incubate the plates and do a viable count.

13. Calculate log₁₀ reductions achieved from the difference in theinitial inoculum and the number of test organisms recovered afterdisinfection with a ClO₂ wipe.

Test variables were as follows.

Test Surface

A flat stainless steel instrument tray.

Test Organism

Spores of Bacillus subtilis var. niger NCTC 10073 freshly prepared bythe method of Beeby & Whitehouse.

Inoculum

The test surface was inoculated with 1×10⁸ spores.

Suspending Fluid

Sterile deionised water.

Disinfectant Concentrations

1. 200 ppm ClO₂ (notional)

2. 300 ppm ClO₂ (notional).

Mixing Times

15+30 seconds.

Wiping Times

15+30 +60 seconds.

Controls

1.1% Hospec general purpose neutral liquid detergent (Young'sDetergents)/Kimcare Medical Wipes (Kimberly-Clark).

2. Sterets Alcowipe: 70% IPA (Seton Prebbles Ltd).

3. Sterile deionised water: Kimcare Medical Wipes (Kimberly-Clark).

Results are given in Table 1.

TABLE 1 Mixing Wiping Exp. Disinfectant/ time time VC VC No. Detergent(seconds) (seconds) Surface Wipe 1 200 ppm ClO₂ 15 15 177 143 2 200 ppmClO₂ 15 30 36 14 3 200 ppm ClO₂ 15 60 10 8 4 200 ppm ClO₂ 30 15 800 3005 200 ppm ClO₂ 30 30 240 27 6 200 ppm ClO₂ 30 60 29 26 7 300 ppm ClO₂ 1515 1240 330 8 300 ppm ClO₂ 15 30 530 250 9 300 ppm ClO₂ 15 60 160 140 10300 ppm ClO₂ 30 15 1450 900 11 300 ppm ClO₂ 30 30 30 70 12 300 ppm ClO₂30 60 20 10 13 1% Hospec 60 7.3 × 10⁴ 4.3 × 10⁵ 14 70% IPA 60 1.9 × 10⁴3.7 × 10⁴ 15 Deionised H₂O 60 2.0 × 10⁵ 3.0 × 10⁵ VC = Viable Count

Interpretation of Results

1. Washing/wiping with water, neutral detergent (1% Hospec), or alcohol(70% IPA) were ineffective

2. For the notional 200 ppm ClO₂ wipes the best results were obtainedwith a mixing time of 15 seconds and a wiping time of 60 seconds.

3. For the notional 300 ppm ClO₂ wipes the best results were obtainedwith a mixing time of 30 seconds and a wiping time of 60 seconds.

4. Results for 200 ppm ClO₂ (notional) were surprisingly better thanresults for 300 ppm (notional), except for mixing times of 30 secondscombined with wiping times of at least 30 seconds.

5. A wiping time of 60 seconds achieved better results than a wipingtime of 30 seconds, which in turn achieved better results than a wipingtime of 15 seconds.

6. Both ClO₂ concentrations achieved good results after a wiping time of60 seconds. The test surface was inoculated with 1×10⁸ spores. Afterusing the ClO₂ wipes, surface counts were reduced to 10 and 29 (200 ppmClO₂) and to 160 and 20 (300 ppm ClO₂).

7. A wipe containing 200 or 300 ppm may be useful, as may mixing timesof 15 or 30 seconds (or, clearly, any intermediate times). However, itis preferred that wiping times longer than 15 seconds are employed.

These results were obtained using bacterial spores. It is to be expectedthat a vegetative bacterium such as MRSA will be much more sensitive, sothat lower ClO₂ concentrations and/or shorter mixing or wiping times maybe effective against such bacteria.

Further experiments (2-4) were carried out using 41 gsm spunlace sheetscomprised of 50.5% wood pulp and 49.5% PET. The sheets' dimensions were160 mm×180 mm×0.36 mm. In each experiment the wipes each contained 3 mlof Solution A (formulated as set forth below), made by treating acanister of 50 wipes with 150 ml of Solution A. Each wipe was activatedwith 1.5 ml of Solution B (formulated as set forth below) from a foamdispenser.

Solution A (Wipe) Formulation: Actual % Ingredients w/w Tolerance 1Citric acid 0.50% +/−0.60-0.40% C.A.S. 77-92-9 2 Sorbic acid 0.005% +/−0.006-0.004% C.A.S. 3 Boric acid 0.005%  +/−0.006-0.0040  C.A.S.10043-35-3 4 Trisodium citrate 0.25% +/−0.30-0.20% C.A.S. 68-04-02 5Trisodium phosphate 0.35% +/−0.45-0.25% C.A.S. 10101-89-0 6 Glycerin1.00% +/−1.10-0.90% C.A.S. 56-81-5 7 Benzotriazole 0.10% +/−0.15-0.05%C.A.S. 95-14-7 8 Sodium molybdate 0.10% +/−0.15-0.05% C.A.S. 10102-40-69 Sodium nitrate 0.20% +/−0.25-0.15% C.A.S. 7631-99-4 10 Preservative(Paramotol) 0.15% +/−0.20-0.10% C.A.S. 11 Deionised water BalanceBalance C.A.S. 7732-18-5

Solution B (Foam) Formulation: Actual % Ingredients w/w Tolerance 1Sodium chlorite (25% solution) 0.75% +/−0.85-0.65% 2 Cocamidopropylbetaine 3.00% +/−3.10-2.90% 3 Indicator/colour solution 0.60%+/−0.07-0.50% (Indicator is cosmetic yellow, No. 5, cl 19140 at 1%solution- 0.6%) 4 Preservative 0.15% +/−0.20-0.10% (Euxyl K 100) 5Deionised Water (Purified) 95.50%  +/− C.A.S. 7732-18-5 Balance

Experiment 2

A study was carried out to compare the effectiveness of (a) ClO₂ wipesin accordance with the invention (b) a 70% IPA wipe (c) a neutraldetergent wipe and (d) a water wipe in removing and/or killing (1) B.subtilis spores, and (2) P. aeruginosa cells dried onto the insertiontube of a flexible endoscope.

Wipes were prepared fresh as required by squirting foam onto a wipe andthen scrunching the wipe with the fingers to mix the reagents to formClO₂.

EXPERIMENT 2 Test Organisms B. Subtilis NCTC 10073 Spores

A suspension containing approximately 10⁸ spores/ml was prepared by themethod of Beeby & Whitehouse. A 1 in 10 dilution in sterile distilledwater was prepared to produce a suspension containing approximately 10⁷spores/ml.

P. aeruginosa NCTC 6749

A culture containing approximately 10⁸ cells/ml was prepared byinoculating a tube of nutrient broth and incubating for 18 h at 37° C.

Insertion Tube Used in Experiment 2

The insertion tube was 1 metre long, in good condition, with clearmarkings. The test site used was the 10 cm section between the 30 and 40markings.

Test Method

1. Immerse a cotton-tipped swab into a suspension of spores orvegetative cells.

2. Inoculate entire surface area of test site with the suspension.Repeat several times. Regarding B. subtilis spores, assume that (1) thevolume of inoculum=0.1 ml, and (2) the mortality rate on drying out iszero. Hence the viable count of the inoculum=approximately 10⁶ spores.Regarding P. aeruginosa cells, assume that (1) the volume ofinoculum=0.1 ml, and (2) the mortality rate on drying out is 1 log.Hence the viable count of the inoculum=approximately 10⁶ cells.

3. Place inoculated insertion tube across the top of an empty discardjar with the 10 cm test site resting over the centre of the jar. Allowinoculum to dry out (approximately 30 minutes).

4. Don pair of disposable plastic gloves.

5. Prepare a Wipe: ClO₂ (scrunch time=15 sec), IPA, Hospec or water.

6. Wipe test site for the prescribed wipe time (30 sec) as follows: Wrapwipe loosely around the insertion tube and then wipe up and down thetest site repeatedly.

7. Place the wipe in 20 ml of universal neutraliser in a Universalbottle. Vortex stir to release recovered spores/cells (Test SuspensionA).

8. Swab entire test site with a cotton-tipped swab. Dip swab into 10 mlof universal neutraliser in a Universal bottle and rotate swab againstthe inner wall of the bottle to release recovered spores/cells. Repeat10 times then break off cotton-tip of swab and leave in the neutraliser.Vortex stir to release recovered spores/cells (Test Suspension B).

9. Prepare 5 serial deci-dilutions of Test Suspension A and TestSuspension B in diluent.

10. Inoculate 0.5 ml of each dilution onto a culture plate and spreadusing a plastic spreader. Incubate plates. Viable count.

11. Calculate log_(ic) reductions achieved from the difference in thenumber of spores or cells inoculated onto the test site (approximately10⁶) and the number recovered after cleaning and/or disinfection.

Wipes used in Experiment 2

1. ClO₂ Wipe (scrunch time=15 seconds).

2. 70% IPA wipe: Azowipe (Vernon Carus).

3. Hospec wipe: Kimberley Clark Medical Wipe immersed in 1% Hospec andthen squeezed to remove excess solution.

4. Water wipe: Kimberley Clark Medical Wipe immersed in sterile waterand then squeezed to remove excess water.

Experiment 2 Results

TABLE 2 Disinfec- Scrunch Wipe Viable Count Test tant/de- time time (0.5ml) Exp organism tergent (sec) (sec) Surface Wipe 1 B. ClO₂ 15 30 0 0 2subtilis ClO₂ 15 30 0 0 (repeat) 3 70% IPA 30 5.0 × 10² 2.7 × 10³ 4 1%30 1.5 × 10² 2.6 × 10³ Hospec 5 Water 30 3.0 × 10¹ 2.5 × 10³ 6 P. ClO₂15 30 0 0 7 aeruginosa ClO₂ 15 30 0 0 (repeat) 8 70% IPA 30 2 0 9 1% 306.2 × 10³ 8.0 × 10⁴ Hospec 10 Water 30 2.5 × 10⁴ 1.5 × 10⁵

TABLE 3 Total spores/cells Disinfectant/ recovered Exp Test organismdetergent Surface¹ Wipe² 1 B. subtilis ClO₂ 0 0 2 ClO₂ (repeat) 0 0 370% IPA 1.0 × 10⁴ 1.0 × 10⁵ 4 1% Hospec 3.0 × 10³ 1.0 × 10⁵ 5 Water 6.0× 10² 1.0 × 10⁵ 6 P. aeruginosa ClO₂ 0 0 7 ClO₂ (repeat) 0 0 8 70% IPA4.0 × 10¹ 0 9 1% Hospec 1.2 × 10⁵ 3.2 × 10⁶ 10 Water 5.0 × 10⁵ 6.0 × 10⁶¹Viable count in Table 1 × 20 (0.5 ml of 10 ml neutraliser plated out).²Viable count in Table 1 × 40 (0.5 ml of 20 ml neutraliser plated out).

Experiment 2 Conclusions

1. ClO₂ wipes were completely effective against both B. subtilis sporesand P. aeruginosa cells. No spores or cells were recovered in duplicateexperiments.

2. IPA wipes exhibited good activity against P. aeruginosa cells but didnot eliminate all of the test cells—40 viable cells were recovered fromthe test site on the insertion tube.

3. IPA wipes were ineffective against B. subtilis spores. IPA provedless effective than 1% Hospec or water which may be attributable to thecoagulant properties of alcohol (fixing spores on the test site).

4. Wipes saturated with 1% Hospec were ineffective against either B.subtilis spores or P. aeruginosa cells.

5. Wipes saturated with water were ineffective against either B.subtilis spores or P. aeruginosa cells.

Experiment 3 Evaluation of the Effectiveness of Clo₂ Wipes inKilling/Removing Methicillin Resistant Staphylococcus Aureus (MRSA)Dried onto a Stainless Steel Test Surface Test Method

The following test method was used to evaluate the effectiveness of ClO₂Wipes in killing/removing test-organisms dried onto test surfaces. Thetest method involves the following steps:

1. Mark out an 18 inch (457.2 mm) square on the test surface.

2. Inoculate test surface with 4.5 ml of test organism suspension.

3. Spread inoculum over 18 inch (457.2 mm) square test area using aplastic spreader.

4. Allow inoculum to dry (30-60 minutes).

5. Don pair of disposable plastic gloves.

6. Prepare a ClO₂ Wipe using the prescribed scrunch time (15 seconds).

7. Wipe test area for the prescribed wipe time (30 seconds).

8. Place the ClO₂ Wipe in 20 ml of universal neutraliser in a universalbottle. Vortex stir to release organisms. (Test Suspension A).

9. Swab entire test area with a cotton-tipped swab. Dip swab into 10 mlof universal neutraliser in a universal bottle and rotate cotton-tipagainst the inner wall of the bottle to release organisms. Repeat 10times. Finally, snap off cotton-tip into the neutraliser. Vortex stir torelease organisms. (Test Suspension B).

10. Prepare 5 serial deci-dilutions of Test Suspension A and TestSuspension B in diluent.

11. Inoculate 0.5 ml of each dilution onto a culture plate and spreadusing a plastic spreader. Incubate plates. Viable count.

12. Calculate log_(ic) reductions achieved from the difference in theinitial inoculum and the number of test organisms recovered aftercleaning/disinfection with a ClO2 Wipe.

13. Repeat above using control wipes (70% IPA, 1% Hospec & sterilewater).

Variables Selected in Experiment 3 Test Surface

A flat stainless steel laboratory bench.

Test Organism

Methicillin Resistant Staphylococcus aureus (MRSA): a clinical isolatefrom the Royal Preston Hospital.

Inoculum

The test surface was inoculated with >10⁹ bacterial cells: 4.5 ml of anovernight culture in Nutrient Broth.

Suspending Fluid

Nutrient Broth

Scrunch Time

15 seconds

Wipe Time

30 seconds

Controls

1.70% IPA wipe: Azowipe (Vernon Carus).

2.1% Hospec general purpose neutral liquid detergent (Young'sDetergents)/Kimcare Medical Wipe (Kimberly-Clark). The wipe was immersedin 1% Hospec and then squeezed with the fingers to remove excess fluid.

3. Sterile deionised water/Kimcare Medical Wipe (Kimberly-Clark). Thewipe was immersed in water and then squeezed with the fingers to removeexcess fluid.

Results

TABLE 4 Mixing Wiping Disinfectant/ time time Viable Count Exp detergent(sec) (sec) Surface Wipe 1 ClO₂ 15 30 0 0 2 ClO₂ (repeat) 15 30 0 0 370% IPA 30 5.5 × 10⁴ 9 4 1% Hospec 30 5.5 × 10⁴ 6.0 × 10⁴ 5 DeionisedH₂O 30 5.7 × 10⁴ 5.9 × 10⁴

TABLE 5 Mixing Wiping Total number of Disinfectant/ time time organismsrecovered Exp detergent (sec) (sec) Surface¹ Wipe² 1 ClO₂ 15 30 0 0 2ClO₂ 15 30 0 0 (repeat) 3 70% IPA 30 1.1 × 10⁶ 3.6 × 10² 4 1% Hospec 301.1 × 10⁶ 2.4 × 10⁶ 5 Deionised 30 1.1 × 10⁶ 2.4 × 10⁶ H₂O ¹Viable Countin Table 1 × 20 (0.5 ml of 10 ml neutraliser plated out). ²Viable Countin Table 1 × 40 (0.5 ml of 20 ml neutraliser plated out).

Interpretation of Results

1. Wiping with a ClO₂ Wipe for 30 seconds was completely effective. Notest organisms were recovered from either the test surface or the wipesin duplicate experiments.

2. Wiping the test surface with a 70% IPA wipe (Azowipe) for 30 secondswas ineffective. This could be due to:

(a) an exposure time of 30 seconds was not long enough to kill the MRSA

(b) the IPA evaporated off the test surface before the minimum exposuretime required to kill the MRSA

(c) the volume of IPA on the wipe was insufficient to deal with the >10⁹MRSA dried onto the 18 inch test surface

(d) a combination of the above.

3. Only 360 test organisms were recovered from the Azowipe. This couldbe due to:

-   (a) entrapment of test organisms in the fibres-   (b) incomplete/slow neutralisation of the residual IPA on the wipe    by the neutraliser-   (c) a combination of the above

4. Wipes saturated with either 1% Hospec or sterile water wereineffective.

Experiment 4

This experiment was carried out to evaluate the effectiveness of ClO₂Wipes in killing/removing spores of Bacillus subtilis var. niger NCTC10073 dried out for 24 h at room temperature on a stainless steel testsurface.

Test Method

1. Mark out a 12 inch (304.8 mm) square on the test surface.

2. Inoculate test surface with 1.0 ml of aqueous spore suspension.

3. Spread inoculum over 12 inch (304.8 mm) square test area using aplastic spreader.

4. Allow inoculum to dry out naturally at room temperature for 24 h.

5. Don pair of disposable plastic gloves.

6. Prepare a ClO₂ Wipe using the prescribed scrunch time (15 seconds).

7. Wipe test area for the prescribed wipe time (30 seconds).

8. Place the ClO₂ Wipe in 20 ml of universal neutraliser in a universalbottle. Vortex stir to release organisms. (Test Suspension A).

9. Swab entire test area with a cotton-tipped swab. Dip swab into 10 mlof universal neutraliser in a universal bottle and rotate cotton-tipagainst the inner wall of the bottle to release organisms. Repeat 10times. Finally, snap off cotton-tip into the neutraliser. Vortex stir torelease organisms. (Test Suspension B).

10. Prepare 5 serial deci-dilutions of Test Suspension A and TestSuspension B in diluent.

11. Inoculate 0.5 ml of each dilution onto a culture plate and spreadusing a plastic spreader.

12. Repeat above using a control wipe (a Medical Wipe saturated withsterile water).

13. Incubate plates. Viable count.

14. Calculate log₁₀ reductions achieved using the ClO2 Wipe from thedifference in viable count obtained using the ClO2 Wipe and the controlwipe.

Variables Selected in Experiment 4 Test Surface

A flat stainless steel instrument tray.

Test Organism

Bacillus subtilis var. niger NCTC 10073. A spore suspension was preparedby the method of Beeby & Whitehouse.

Inoculum

The test surface was inoculated with (a) 10 6 spores, and (b) 10⁸spores.

Suspending Fluid

Deionised water.

Drying Time

The inoculated instrument tray was allowed to dry out naturally at roomtemperature for 24 h in a dark cupboard.

Scrunch Time

15 seconds.

Wipe Time

30 seconds.

Control

1. Sterile deionised water/Kimcare Medical Wipe (Kimberly-Clark). Thewipe was immersed in water and then squeezed with the fingers to removeexcess fluid.

Results

TABLE 6 Inoc- Mixing Wiping ulum Disinfectant/ time time Viable CountExp. (spores) detergent (sec) (sec) Surface Wipe 1 10⁶ ClO₂ 15 30 0 0 210⁶ Water 15 30 2.0 × 10² 2.1 × 10² 3 10⁸ ClO₂ 15 30 4.8 × 10² 1.3 × 10²4 10⁸ Water 15 30 6.6 × 10⁴ 1.9 × 10⁵

TABLE 7 Mixing Wipe Total number of Inoculum Disinfectant/ time timespores recovered Exp. (spores) detergent (sec) (sec) Surface¹ Wipe² 110⁶ ClO₂ 15 30 0 0 2 10⁶ Water 15 30 4.0 × 10³ 8.4 × 10³ 3 10⁸ ClO₂ 1530 9.6 × 10³ 5.2 × 10³ 4 10⁸ Water 15 30 1.3 × 10⁶ 7.6 × 10⁶ ¹ViableCount in Table 1 × 20 (0.5 ml of 10 ml neutraliser plated out). ²ViableCount in Table 1 × 40 (0.5 ml of 20 ml neutraliser plated out).

Interpretation of Results

1. Spores dried out for 24 h at room temperature on a stainless steeltest surface were not easy to dislodge using a Medical Wipe saturatedwith deionised water. With the 10⁶ inoculum the recovery was 4.0−8.4×10³spores leaving 2-3 log₁₀ spores on the surface (assuming no mortality).With the 10⁸ inoculum the recovery was 1.3−7.6×10⁶ spores leaving 1-2log_(ic) spores on the surface.

2. ClO₂ Wipes were effective in killing/removing spores dried out for 24h at room temperature on the stainless steel test surface. With the 10⁶inoculum, no spores were recovered from either the surface or wipe whichrepresents a 3-4 log_(ic) reduction on both the surface and wipe. Withthe 108 inoculum, a 2-3 log₁₀ reduction of spores was achieved on thesurface and a 3-4 log₁₀ reduction on the wipe.

Thus, the invention provides a sterilant system which can be prepared insitu and which provides bactericidal, fungicidal, virucidal, andsporicidal fabrics. The system is particularly useful for sterilisingwipes and for the dressing of wounds and ulcers.

To promote and accelerate the production of ClO₂ from the solutions wehave found that acetic anhydride and ascorbic acid may advantageously beemployed together as additives in Solution A. A preferred concentrationfor each additive is 0.4%

It is appreciated that certain features of the invention which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention which are, for brevity, described in thecontext of a single embodiment, may also be provided separately, or inany suitable combination. It is to be recognized that variousalterations, modifications, and/or additions may be introduced into theconstructions and arrangements of parts described above withoutdeparting from the spirit and scope of the present invention. As usedherein, the indefinite articles ‘a’ and ‘an’ connote ‘one or more’unless the context requires otherwise.

I claim:
 1. A two-part sterilant system comprising: (a) a first partcomprising a first reagent in a carrier medium; and (b) a second partwhich is miscible with the first part and which comprises a secondreagent in a carrier medium; wherein the first reagent and the secondreagent will react when mixed to provide a sterilising composition;wherein the first part is a fluid which includes a foam promoter and iscontained in a trigger-operated foam dispenser constructed fordispensing the first part as foam; wherein the second part is absorbedor impregnated in at least one fabric wipe containing an aqueous fluidin a sealed container.
 2. A sterilant system according to claim 1,wherein the at least one fabric wipe comprises a plurality of fabricwipes, each of which is provided in its own separate sealed sachet.
 3. Asterilant system according to claim 1, wherein at least one of the firstpart and the second part includes an indicator reagent that changescolour when the parts are mixed together.
 4. A sterilant systemaccording to claim 3, wherein the first part and the second part have adifferent pH and wherein the indicator reagent changes colour inresponse to a change in pH when the parts are mixed.
 5. A sterilantsystem according to claim 1, wherein one of the first part and thesecond part comprises a solution containing sodium chlorite or sodiumchlorate and the other comprises an acidic solution.
 6. A sterilantsystem according to claim 5, wherein the acidic solution comprises asolution of citric acid, sorbic acid and boric acid.
 7. A sterilantsystem according to claim 1, wherein the foam promoter is present in anamount from 0.1 to 50% w/w of said first part.
 8. A sterilant systemaccording to claim 7, wherein said foam promoter is present in an amountfrom 3 to 6% w/w of said first part.
 9. A sterilant system according toclaim 1, wherein one of the first part and the second part furthercomprises from 0.1 to 50% w/w of a humectant.
 10. A sterilant systemaccording to claim 1, wherein said humectant is present in an amountfrom 1 to 3% w/w of said first part or said second part.
 11. A sterilantsystem according to claim 1, wherein when equal weights of the firstpart and the second part are mixed they provide a sterilisingcomposition having a pH of from 4.5 to 6.5.
 12. A sterilant systemaccording to claim 5, wherein the first part comprises said solution ofsodium chlorite or sodium chlorate.
 13. A sterilant system according toclaim 12, wherein said first part comprises a solution of sodiumchlorite and said acidic solution comprises an aqueous mixture of citricacid, sorbic acid, boric acid, and a buffer.
 14. A sterilant systemaccording to claim 1, wherein one of the first reagent and the secondreagent comprises chlorite and the other comprises hypochlorite.
 15. Asterilant system according to claim 1, wherein one of the first reagentand the second reagent comprises chlorate and the other comprises aperoxide and an acid.
 16. A sterilant system according to claim 1,wherein the at least one fabric wipe comprises a plurality of fabricwipes interleaved in a resealable container.
 17. A two-part sterilantsystem comprising: (a) a first part comprising a first reagent in acarrier medium; and (b) a second part which is miscible with the firstpart and which comprises a second reagent in a carrier medium; whereinthe first reagent and the second reagent will react when mixed toprovide a sterilising composition; wherein the first part is a gel andis contained in a trigger-operated dispenser constructed for dispensingthe first part as a gel; wherein the second part is absorbed orimpregnated in at least one fabric wipe containing an aqueous fluid in asealed container.
 18. A sterilant system according to claim 17, whereinthe at least one fabric wipe comprises a plurality of fabric wipes, eachof which is provided in its own separate sealed sachet.
 19. A sterilantsystem according to claim 17 wherein the at least one fabric wipecomprises a plurality of fabric wipes interleaved in a resealablecontainer.
 20. A two-part wound-dressing system comprising: (a) a firstpart comprising a first reagent in a carrier medium; and (b) a secondpart which is miscible with the first part and which comprises a secondreagent in a carrier medium; wherein the first reagent and the secondreagent will react when mixed to provide a sterilising composition;wherein the first part is a fluid which includes a foam promoter and iscontained in a trigger-operated foam dispenser constructed fordispensing the first part as a foam; wherein the second part is absorbedor impregnated in at least one fabric wound dressing containing anaqueous fluid in a sealed container.
 21. A wound-dressing systemaccording to claim 20, wherein the at least one fabric wound dressingcomprises a plurality of fabric wound dressings, each of which isprovided in its own separate sealed sachet.
 22. A wound-dressing systemaccording to claim 20, wherein the at least one fabric wound dressingcomprises a plurality of fabric wound dressings interleaved in aresealable container.
 23. A two-part wound-dressing system comprising:(a) a first part comprising a first reagent in a carrier medium; and (b)a second part which is miscible with the first part and which comprisesa second reagent in a carrier medium; wherein the first reagent and thesecond reagent will react when mixed to provide a sterilisingcomposition; wherein the first part is contained in a pump dispenserconstructed for dispensing the first part as a gel; wherein the secondpart is absorbed or impregnated in at least one fabric wound dressingcontaining an aqueous fluid in a sealed container.
 24. A wound-dressingsystem according to claim 23, wherein the at least one fabric wounddressing comprises a plurality of fabric wound dressings, each of whichis provided in its own separate sealed sachet.
 25. A wound-dressingsystem according to claim 23, wherein the at least one fabric wounddressing comprises a plurality of fabric wound dressings interleaved ina resealable container.